1. Field of the Invention
The invention relates to valves and valve actuation, especially to valve actuators used on blow out preventers. More specifically, the invention relates to fluid actuated or retarded valve operation, wherein the valve is rotating relatively to the actuator or to a portion of the actuator or to a structure connected to the actuator.
2. Description of the Prior Art
In applications wherein a valve is physically rotated, as in combination with another apparatus, a problem is created when it is desired to open or close the valve. Specifically, in oil well drilling rigs a valve is located atop the kelly, also known as the drill string tubing, which is typically a square shaft rotated with the drill bit. This valve is known as the upper kelly valve. At the top of the kelly valve is connected the kelly swivel, which is an attachment point for a hose used to pump drilling mud through the kelly valve, through the kelly, and thus into the well hole to contain the pressures encountered at great depths in the well.
During the drilling of a well if a pressure is encountered that is capable of reverse flowing the drilling mud from the bid upwardly through the kelly and upper kelly valve, a "blowout" may occur, wherein the gases within the well escape. When such pressures successfully escape upwardly through the upper kelly valve, the mud hose may be blown off the swivel, after which a spark may ignite the gases. One purpose of the upper kelly valve is to prevent such a sequence of events from occuring, although this purpose is hindered by the remote location of the upper kelly valve, often forty feet above the ground. In the past most kelly valves have been manually actuated, requiring both that the rotation of the valve be stopped and that a person physically approach the valve before the valve can be closed.
Various devices have been built to remotely close the upper kelly valve, although none are known to have been entirely satisfactory. It is necessary for a remote valve actuator used on an oil drilling rig to be extremely reliable, resistent to dirt and rough handling, and easily adaptable to power sources that are commonly used with such rigs.
The present invention solves these and other problems as is more fully explained below.